Tapes



Dec. 6, 1955 F. F, NEwKlRk 2,725,133

TAPES Filed NOV. 5, 1951 INVENTOR FRANCIS F. NEWKIRK "ATTORNEY TAPES Francis F. Newkirk, Attleboro, Mass., assignor, by mesne assignments, to American Sisalkraft Corporation, a corporation of Delaware Application November 3, 1951, Serial No. 254,685

6 Claims. (Cl. 154-535) This invention relates to the packaging art and particularly to stay tapes used in the manufacture of boxes and cartons. Its object is to provide an improved laminated paper tape which is especially adapted for securing together the manufacturers joint of a berboard box, and which is so constructed as to assure that the strength imparting elements of the tape responsible for the security of the joint will remain in place over the joint despite rough treatment of the box at and adjacent the joint tending to strip away portions of the tape.

In accordance with this invention a box stay tape made of a lamination of paper plies adapted to be secured to a box corner by a Water moistenable gum interposed between the box and the backing ply of the tape, has its backing ply permeated with a material which greatly enhances the interber bond strength of the ply, as evidenced by its resistance to laminar separation internally of the ply. Heretofore box joint failures were in many instances attributable to a peeling or tearing away of the outer portions of the tape by a cleavage or internal separation of the backing ply into layers, with one layer remaining adhered to the box and the other layer peeling away with the remainder of the tape. The present invention, by enhancing the interber cohesion of the backing ply, affords an eiective solution to the problem, greatly increasing the durability of the manufacturers joint. My experiments have shown that the prior teachings of the art as to the enhancement of the tensile strength, tear strength, burst strength and other conventional strength standards alford no true criteria for the enhancement of resistance to laminar separation stress fundamental to the present invention.

In the drawings:

Fig. l is an enlarged diagrammatic section through the manufacturers joint of a fiberboard box secured together in accordance with this invention, shown in position before the box has been set up, and Fig. 2 is a perspective view of the joint after the box has been set up, partly broken away to show the tape plies.

The box joint of Fig. 1 presents box sides 10 and 12 to be joined. Over the joint is extended a layer of glue 14 contacting the box surface, followed by a ply of kraft paper 16, uniformly impregnated with a limited quantity of cellulose derivative 18, to be referred to, followed by a layer of moisture impermeable resinous adhesive, asphalt or the like in which reenforcing strandsv 22 extending transversely of the joint are preferably embedded. The covering sheet 24 is also of kraft and may be creped to give stretchability when the box is set up. The ply 24 need not be impregnated as is the backing ply 16.

The purpose of the joint construction provided by the present invention is to assure that despite rough handling of the box, the several elements of the tape will remain in place spanning the joint so that their strength is available to hold the joint secure. To that end the fibers of the paper ply 16 are secured together'by the impregnant 18 so that the sheet 16 has an interiiber bond strength which resists separation of the fibers under stresses when the box corner is scuied or otherwise so abused in use as to tend to strip away the tape by laminar separation of the ply 16. My experiments have shown that the impregnant 18 supplies the needed inter-V iber bond strength, in a unique way,Y to'that element which has heretofore been the weakestpart of a box joint. Thus, in vthe construction shown, under externally applied stress tending to separate the tape elements from each other orrfrom the box, the ply 24 isA not stripped from the resinous adhesive 20; the strands 22 do not separate from the adhesive 20 which in turn does not separate from the surface of ply 16; the glue 14 is not dislodged from either the box or the ply 16. Thel stress resulting from the yresistance of these elements to separation is taken internally of the ply 16 and by the present invention'those stresses are effectively vresisted by the impregnant 18 so that the service life of a box joint is thereby greatly increased.

The impregnant 18 has a number of important characteristics both as to its eifect on the plyr16 and as to its eiect on the other elements of theA tape.

The ply 16, by virtue of the impregnant 18, has a high interber bond strength. This property is not reliably indicated by the conventional accepted paper tests such as tensile strength, bursting strength, tear values, and the like. On the contrary, there is no apparent'correlation between such values and the interber bond strength which is significant of the resistance of the paper ply to laminar separation. In practice, I test for intertiber bond strength by securely adhering one surface of a small test sheet of the impregnated paper,

when dry, to an immovable base and securely adhering the opposite surface to an element such as an angle iron which, upon being struck with sufficient force, will move so that the sheet is split into layers. The energy consumed in splitting the sheet is an accurate measure of its interiiber bond strength. In general, the greater the interber bond strength, the better the paper is for my purposes, except that the nature and quantity of the irnpregnant used must not be such as to aiect adversely the tape combination in other respects. Thus, the permeability ofthe ply to adequate surface absorption of water moistenable gum 14 on one face and resinous type adhesive 20 on the other, sufhciently to aiord a goodl bond, must be retained, and to that end the quantity of the impregnantthat may be used is'limited. The

impregnant must not be deleteriously aiect the other elements which it contacts, and for that reason formaldehyde-type wet strength imparting agents which tend lto solids form a tough pliable iilm of high adhesive tenacity to the paper ber.

Where the cellulose derivative is soluble in water, it is added directly to the beater and becomes dissolved in the water in which the pulp is'dspersed. Where the cellulose derivative is insoluble` in Water, itis rst dispersed in water, or first dissolved'in a solvent in which it is soluble, and then dispersed in water Vas an emulsion or a gel, the concentrated dispersion or emulsion then being added to the beater where it is evenly `mixed with the paper pulp.

Among the suitable water soluble cellulose derivatives Patented` Dec. 6, 1955 are the lower aliphatic ethers, such as methyl cellulose, hydroxy ethyl cellulose, alkali metal salts of carboxy methyl cellulose such as sodium, potassium, lithium or ammonium salts of carboxy methyl cellulose, and viscose, or alkali cellulose xanthate, and cupra ammonium cellulose.

Among the suitable water insoluble cellulose derivatives are esters of'organic and inorganic A(i. e. mineral) acids. These include cellulose acetate, cellulose propionate, cellulose butyrate and mixed acylation products such as the acetate butyrate or acetate propionate `and higher esters such as benzyl cellulose and esters of higher fatty acids. Among the mineral esters may be mentioned the cellulose nitrate and cellulose sulfate. Certain of the insoluble metal salts of carboxy methyl cellulose, such as barium, calcium, magnesium, or other metal salts, may be used. Similarly, it is possible to use degradation products of a hydrolytic character of cellulose such as well-beaten and gelatinous alkali cellulose. Finally may be mentioned in this group higher insoluble ethers of cellulose such as ethyl cellulose, as well as gelatinous regenerated cellulose. Any of these several cellulose derivatives or mixtures thereof added in the requisite proportion to the beater are readily distributed homogeneously either as a dispersion or solution in the beater water to coat evenly the wet pulp fiber. Upon further processing of the cellulose treated pulp to form paper in conventional manner, the paper is found to have retained its normal surface permeability while having its interiiber bond strength substantially increased as compared with untreated paper.

Cellulose derivatives as described herein have no adverse eiect upon the bonding strength or normal properties of the adhesive, either a water moistenable animal glue type adhesive on one side of the backing ply, or the water impenetrable laminating resinous or asphaltic type adhesive applied to the other side to bond it tol other plies in the formation of the laminated paper tape. For example, such treatment of the paper has no tanning effect upon the water moistenable glue such as frequently results from applying resinous impregnants to paper to improve the wet strength, such resinous impregnants often containing reactive aldehyde radicals which tan and render the glue insoluble.

In the practice of this invention, water insoluble cellulose derivatives are preferably used, but water soluble cellulose derivatives which are readily precipitated in the beater such as viscose, alkaline salts of carboxy methyl cellulose, hydroxy ethyl ether of cellulose may also be used. Such water soluble compounds are readily precipitated in the aqueous bath by acidification, i. e. change ofpH to the range of 3 to 6, or by addition of precipitating salts which convert a soluble alkaline cellulose salt to an insoluble salt. Salts such as alkaline earth metal chlorides, i. e. barium, calcium or magnesium chlorides or soluble sulfates, may be added to the beater, of which ordinary paper makers alum is the most practical precipitating agent.

Where the cellulose derivatives are water soluble and diicult to precipitate in the beater, much of the compound may be lost by remaining dissolved in the beater water when the pulp is separated from it in the formation of paper. Hence, much larger quantities, to give retained impregnant in an amount falling within the above ranges, would be required. Such compounds accordingly are much less economical to use.

The following examples illustrate the practice of the invention.

Example Iy A viscose solution is acidified with mineral acid such as dilute hydrochloric acid to form a gelatinous mass of regenerated cellulose. This is added to the beater, in which paper pulp is being beaten, in the proportion of 2% `dry .weight of gelatinous regenerated cellulose based upon `the dryweight content ofthe cellulosepulp in the beater. The pulp is formed into kraft paper in the usual Way, the paper is assembled as shown in the drawings by bonding with at least one additional ply of another paper, preferably kraft, and which may, but need not, have the same cellulose treatment. The laminate is bonded with an asphalt bonding agent as is conventional in the art, such as described in U. S. patent to Newkirk No. 2,089,405, dated August l0, 1937, or preferably with the improved resinous type agent disclosed in the Nickerson application Serial No. 149,641, filed March 14, 1950. Thereafter, the dry bonded laminate is coated in a gumming machine with conventional water moistenable animal glue applied to the outer face of the ply which has been treated with the cellulose, the glue thereafter being dried, and the tape is then ready for use as a box stay tape, according to the present invention, having highly increased interlibcr bond strength in its backing ply.

The adhesive disclosed in the said Nickerson application is a hot coating emulsion formed by mixing a latex of elastomer particles suspended in water with a heat liquied resinous plasticizer compatible with the elastomer which is thermoflowing at raised temperatures below 212 F.V The plasticizer forms the continuous phase of the emulsion, and the latex forms the disperse phase. After the paper has been hot coated with the adhesive and adhered to another sheet to form a laminate, water is absorbed from the emulsion by the paper so that the adesive sets to a highly viscous and tacky gel which is flexible and non-staining and will not bleed through the paper. Proportions useful are in the range of l to l0 parts of resin to l part of elastomer.

The construction of the laminate may be modified by creping the outermost ply of paper, which does not bear the glue coating. Reenforcing strands or fibers such as sisal or glass may embedded within the resinous bond to improve the strength of the tape according to practices known in the art.

ln this example, the viscose was rst regenerated to the gelatinous form of the cellulose and then dispersed in the beater. However, a similar strengthening effect may be obtained by adding the same quantity of soluble alkaline viscose, i. e. water soluble sodium cellulose xanthate, directly to the beater to form a homogeneous solution in the beater water and thereafter precipitating the xanthate in situ on the pulp in the beater either by acidification of the beater water, or by addition thereto of a solution of a precipitating salt such as alum. Either operation effects quantitative precipitation and regeneration `of the cellulose in situ upon the pulp ber in the beater.

Example Il lf it is desired to use water insoluble cellulose derivatives, for example ethyl cellulose, a dispersion may be prepared by mixing the ethyl cellulose in a Banbury mixer or on a rubber mill with an equal quantity of a plastcizer consisting of 50% castor oil and 50% dioctyl phthalate. To this mixture is added a 10% ammonium caseinate solution in an amount sufficient to give 5% ammonium easeinate based on the total weight of ethyl cellulose plus plastieizer. Following this, 5% oleic acid is also added. Dilute ammonia water is then worked into the mix until an oil in water type of dispersion is obtained. This dispersion may then be added to paper pulp in the beater in an amount sufficient to give the desired amount, for example about 5%, of the ethyl cellulose plasticizer mixture based on the dry paper liber within the above ranges.v

Similarly, other cellulose derivatives such as higher cellulose ethers, cellulose esters of both organic and mineral ester types, may be dissolved in an organic solvent and the solution thereof then dispersed as fine droplets of gelled cellulose derivative and applied to the pulp beater as described.

Example III Sodium carboxy methyl cellulose as a solution in water is added to kraft paper pulp in the beater and a homogeneous solution formed in the beater water, the proportion being 2Vz% of sodium carboxy methyl cellulose based upon the dry weight of the paper pulp in the beater. Thereafter, a stoichiometric quantity of paper markers alum in relation to the soluble cellulose derivative dissolved in water as a solution of the alum is added to the beater Water so that the carboxy methyl cellulose precipitates in the beater in situ upon the pulp and the pulp thereafter is formed into paper which becomes the backing ply of the paper tape formed therefrom as described in Example I. In a similar manner, an alkaline solution of hydroxy ethyl cellulose may be applied to the pulp in the beater and the hydroxy ethyl cellulose precipitated in situ upon the pulp by addition to the beater water of suicient acid.

As thus described, any non-fibrous cellulose compound may be added to the beater in the manufacture of a paper which is to become the backing ply of a laminated paper tape which will bear on one surface a water moistenable glue for adhesion to a paper box. Such treatment materially increases the resistance of such tape to laminar separation when dry and the permeability of the paper to the adhesives which it contacts is substantially unimpaired.

This application is a continuation-impart of my prior co-pending application Ser. 649,367, now abandoned.

I claim:

1. Box stay tape comprising a plurality of paper plies bonded together with asphalt and having an exposed face coating on one of the outermost plies of dry animal glue, the paper ply carrying said animal glue having its libers coated with a dry cellulose compound selected from the group consisting of gelatinized regenerated cellulose, vis

cose, hydroxy ethyl ether of cellulose, methyl cellulose, ethyl cellulose, carboxy methyl cellulose, metal and ammonium salts of carboxy methyl cellulose, cupra ammonium cellulose, alkali cellulose xanthate, and mixtures thereof, said cellulose compound being contained in the paper in proportion of 1/2 to 10% by weight thereof and applied thereto by addition to the wet paper pulp in the beater during manufacture of the paper whereby the ce1 lulose compound coats the bers of the paper without substantially reducing the porosity of the paper.

2. Box stay tape as delned in claim l wherein the cellulose compound is viscose.

3. Box stay tape as defined in claim 1 wherein the cellulose compound is an alkali metal salt of carboxy methyl cellulose.

4. Box stay tape as defined in claim 1 wherein the cellulose compound is ethyl cellulose.

5. Box stay tape as defined in claim 1 wherein the cellulose compound is gelatinized regenerated cellulose.

6. Box stay tape as dened in claim 1 wherein the cellulose compound is methyl cellulose.

References Cited in the le of this patent UNITED STATES PATENTS 1,195,430 Angier Aug. 22, 1916 1,278,935 Jackson Sept. 17, 1918 1,745,557 Richter et al Feb. 4, 1930 2,024,224 Humphner Dec. 17, 1935 2,024,600 Richter et al Dec. 17, 1935 2,026,194 Smith Dec. 31, 1935 2,033,481 Richter Mar. l0, 1936 2,054,115 Abrams et al Sept. 15, 1936 2,089,405 Newkirk Aug. 10, 1937 2,393,553 Musset et al. Jan. 22, 1946 

1. BOX STAY TAPE COMPRISING A PLURALITY OF PAPER PLIES BONDED TOGETHER WITH ASPHALT AND HAVING AN EXPOSED FACE COATING ON ONE OF THE OUTERMOST PLIES OF DRY ANIMAL GLUE, THE PAPER PLY CARRYING SAID ANIMAL GLUE HAVING ITS FIBERS COATED WITH A DRY CELLULOSE COMPOUND SELECTED FROM THE GROUP CONSISTING OF GELATINIZED REGENERATED CELLULOSE, VISCOSE, HYDROXY ETHYL ETHER OF CELLULOSE, METHYLE CELLULOSE, ETHYL CELLULOSE, CARBOXY METHYL CELLULOSE, METHYL CELLULOSE MONIUM SALTS OF CARBOXY METHYL CELLULOSE, CUPRA AMMONIUM CELLULOSE, ALKALI CELLULOSE XANTHATE, AND MIXTURES THEREOF, SAID CELLULOSE, COMPOUND BEING CONTAINED IN THE PAPER IN PROPORTION OF 1/2 TO 10% BY WEIGHT THEREOF AND APPLIED THERETO BY ADDITION TO THE WET PAPER PULP IN THE BEATER DURING MANUFACTURE OF THE PAPER WHEREBY THE CELLULOSE COMPOUND COATS THE FIBERS OF THE PAPER WITHOUT SUBSTANTIALLY REDUCING THE POROSITY OF THE PAPER. 